Enrollment of any patient who has satisfactorily participated in Amgen BDNF 930121 Part C through 9 months without evidence of intolerable toxicity to study drug. Patients will be treated with r-metHuBDNF at the same blinded dose level assigned to them in Amgen BDNF 930121 Part C. Previous placebo patients will be randomized at a l:l ratio blocked by center to receive either 25ug/kg or 100 ug/kg r-metHuBDNF. R-metHuBDNF will be given once daily by subcutaneous injection for up to 24 months in the absence of drug-induced toxicity.